A presentation that allows students to explore
details of the carbon cycle, looking at various parts of this
biogeochemical sequence by examining carbon reservoirs and
how carbon is exchanged among them and the atmosphere.

Carbon is present in every living thing on
Earth ... in one form or the other. It's also present in rocks,
in our air, and in our oceans. The amount of carbon in our
universe is constant... the same today as it was 10,000 years
ago.

Carbon naturally moves throughout our environment in a biogeochemical
cycle called the carbon cycle. Much like the water cycle,
this process is a continual movement of carbon from sources
where carbon is released -- to sinks where carbon is taken
up. Sources can be just about anything, including living things,
our oceans, our lands, and our atmosphere. Sinks include
plants, our land and our oceans.

The process includes:
Photosynthesis: plants pull carbon
in the form of carbon dioxide from the air to use in creating
their own food.
Death and decomposition:
Animals eat plants
and the carbon in plants is transferred to them. When animals and plants die, their carbon is used by decomposers: primarily bacteria and fungi. If there is more carbon than the decomposers can handle, the carbon remains in the earth and substances like coal and oil are formed.
Respiration: Animals and plants release carbon dioxide as they
carry out life processes.

The problem is that human activities are changing this natural
cycle, increasing the amount of carbon in the atmosphere. In the slide show it is noted that there is more carbon dioxide in the atmosphere now than at any point in the last 420,000 years. Although four hundred and twenty thousand years is simply the limit of reliable estimates, there is evidence that even 600,000 years ago levels weren’t as high as they are today.
Development of previously unused land accounts for some of
the increase. But, burning of fossil fuels for transportation,
heat, electricity and other energy needs has had the most
significant impact on the natural carbon cycle. And the effects
of this usage are huge: humans have burned so much fossil
fuel that there is about 30% more carbon dioxide in our atmosphere
today than there was 150 years ago.

All Earth processes are the result of energy
flowing and mass cycling within and between Earth's systems.
(NSF
3.2)

The carbon cycle influences climate in a
variety of ways, including seasonal interactions between
the atmosphere, biosphere, and hydrosphere, and the formation
and consumption of fossil fuels. Carbon dioxide, an important
greenhouse gas, is removed from the atmosphere in the ocean
and other parts of the Earth system through biologic and
geologic processes. (NOAA
4d)

Relatively small increases in amounts of
greenhouse gases-such as carbon dioxide, methane, nitrous
oxides and some refrigerants-can magnify the greenhouse
effect. (NOAA
4g)

The increased burning of fossil fuels since
the start of the industrial revolution has increased the
amount of greenhouse gases in the atmosphere. Because carbon
dioxide remains in the atmosphere for many years (hundreds
to thousands of years) before being removed by natural processes,
this has contributed to Earth's warming. (NOAA
6d)

The Stuff of Life
Before students experience this presentation, involve them
in this activity: To truly understand the carbon cycle,
students might benefit from a discussion about the nature
of carbon, one of the most abundant elements in the universe.
Wikipedia
has a good introductory article that can help you prepare
for this discussion. This timeline
of the history of carbon might be helpful as well.

Photosynthesis Before
students experience this presentation, involve them in this
activity: The sequences of plant and animal respiration figure
significantly in the carbon cycle. How well do your students
understand photosynthesis and the exchange of carbon dioxide
and oxygen between animals and plants? This primer
might help you prepare to explore this topic with your students.
This student-based activity
scaffolds learning for beginner, intermediate, and advanced
learners. It could help your students explore photosynthesis
on their own.

Cycles After students
experience this presentation, involve them in this activity:
Scientists describe the flow of certain substances through
our environment as cycles. The carbon cycle has a great deal
in common with other cycles, such as the water
cycle and the nitrogen
cycle. Direct students to investigate all three cycles
to determine differences and similarities among the three.